This invention relates generally to hot runner injection molding and more particularly to valve gated injection molding apparatus wherein each heated nozzle has a number of valve pins extending therethrough and a central melt bore in which the melt splits near the front end of the nozzle to flow through removable nozzle inserts aligned with the gates.
As seen in U.S. Pat. No. 5,094,603 to Gellert which issued Mar. 10, 1992, it is known to split an injection hot runner at or near the rear end of a heated nozzle. Another example is shown in U.S. Pat. No. 5,368,470 to Manner which issued Nov. 29, 1994 wherein several valve pins are driven by a common piston drive. However, having the hot runner split near the rear end of the heated nozzle has the disadvantage that the split runners extending through the nozzle are smaller which produces more stress in the melt.
DE 37 33 363 shows a hot runner which splits closer to the front end of the nozzle, but it has the disadvantage that there are no individual nozzle inserts that can be made of a more suitable material and are removable for cleaning or replacement if the need arises.